Drowned Sensors

When I described myself on this blog, I said that I don't currently use a continuous glucose monitoring system, and I think you deserve an explanation.

Over a decade ago, when I started using an insulin pump (Medtronic), I tried using its associated monitoring system (Guardian). It turned out that at the time, the equipment wasn't "accurate enough." There I was in the early hours of the morning with a fire-like alarm telling me my glucose was too high. In fact, when I checked this speculation with my glucometer, not only was there no emergency, but my glucose level was right on target: let's say, 98 mg/dL. This happened so frequently that it was starting to bother me.

Strapping an additional device to your pump to cope with repeated false alarms isn't much fun. My doctor at the time and I agreed that as long as I continued using my glucose meters frequently and conscientiously, entering that information into the pump, "everything would be fine and there wouldn't be any major problems." And indeed, that's what we did, and my pump and my manual monitoring worked together wonderfully for years.

Sometime after that, I suddenly decided that it might be a good option to change my treatment, let's say, a bit radically; that is, to put aside the insulin pump for a while and return to treatment with glargine and lispro insulins. Thus, after almost 12 years, I would return to a system of multiple injections per day. I discussed it with my doctor here in Puerto Vallarta, who, knowing that "my discipline would work well under any regimen," gave his approval. I then switched to the FreeStyle Libre continuous blood glucose monitoring system. I went so far as to change my cell phone – from a Samsung Galaxy, which I had used for years, to an Apple iPhone – so I could use it with my new FreeStyle Libre system. I clarify that the latter was a "personal preference" because the FreeStyle Libre system actually has the option of including its own independent reader device. The result wasn't as successful as I had imagined.

Swimming is one of my passions and a very important element in my diabetic treatment. So, when I started using the FreeStyle Libre sensors, which are supposed to stay on the skin for about 14 days, I discovered that they wouldn't stay attached to my body for more than seven days. The first one drowned on the sixth day, and the second suffered the same fate on the seventh.

Since I'm frequently in the water, whether in the pool or the ocean, these sensors couldn't keep up with that pace. In part, I could have expected this because my self-adhesive insulin pump cannulas have occasionally perished from the same cause. However, they are designed to last only four or five days, not 14. It only took a few backstroke laps for me to start feeling something strange in my arm; the sensors would begin to detach after a few minutes in the pool. I decided right then and there to stop using the FreeStyle Libre continuous monitoring system.

Some of you will surely argue that I could have used a bit of adhesive tape around the FreeStyle Libre sensors. But for me that should be a very radical option, required because I'm swimming under special or very aggressive conditions (sand, greater depth, competitions), but these "adhesion failures" occurred while I was swimming quite standardly in a pool, not under the generally more adverse conditions I encounter in the ocean. This proved, once again, that many complex and variable factors affect diabetes treatment and that it must be constantly tailored to the individual. For patients who don't swim, continuous monitoring with the FreeStyle Libre is probably an ideal option; for me, who spends a lot of time in the water, it wasn't.

I must add that I think Abbott's insistence on only recommending the use of its sensors on the arm became part of the problem. This is because if there were more options for places to "hide" and protect the sensor from the force of the water – for example, on the buttocks under a swimsuit, as I do with insulin cannulas – I certainly wouldn't encounter the detachment problem that forced me to abandon the product altogether.

As we've said before, there are many factors involved in treatment, all of which are determined by the very personal and unique characteristics of each diabetic.